Starting circuit for mercury lamps



y 1955 c. M. RlVELY 2,708,251

STARTING CIRCUIT FOR MERCURY LAMPS Filed March 19, 1953 LAMP ATTORNEY United States Patent STARTING CIRCUIT FOR MERCURY LAMPS Clair M. Rively, Rockaway, N. J., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application llrlarch 19, 1953, Serial No. 343,376

6 Claims. or. 315-183) This invention relates to starting circuits for lamps which contain ionizable atmospheres and more particularly to those lamps which have cold cathodes.

As is well known, the voltage required to ignite a lamp having an ionizable atmosphere is much higher than the voltage required to maintain operation after the lamp has once been started. To improve the starting characteristics, most of such lamps are provided with heated cathodes. By heating the cathodes, the electron emission is greatly improved and because of the initial high velocity of the emitted electrons, lower starting voltages are required.

An object of this invention is to provide a circuit for supplying a high voltage to lamps containing ionizable atmospheres, which circuit is reliable, fully automatic, and does not require mechanical switches.

Other advantages and objects of this invention will become evident as the description proceeds.

Referring now to the single figure of the drawing, a lamp 11 containing an ionizable atmosphere (gas or vapor or a combination of the two) is fed from a source of alternating current 12 by the leads 13 and 14 through an inductive ballast 15. Connected between the leads 13 and 14 and in parallel with the lamp 11 is a series circuit comprised of the primary 16 of an iron-core step-up transformer 17 and a capacitor 19 which is of a value to resonate with the primary 16 at the frequency and voltage of the supply source 12. The secondary 18 of the transformer 17 has in parallel with it a capacitor 21, and in series with the secondary 18 and capacitor 21 is a spark gap 22 having a capacitor 23 in parallel with it. The secondary 13 is connected by a lead 25 with one side of the ballast 15, and the spark gap 22 is connected through a lead 24 to the other side of the ballast 15. It will be observed that the series circuit of the secondary 18 and the spark gap 22 each with its own parallel capacir tor forms a loop 20 which includes the ballast 15.

The lamp 11 requires a voltage higher than that of source 12 for starting but means must be provided for limiting the current through the lamp 11 once it lights. The ballast provides a voltage drop and therefore lowers the voltage available at the lamp during normal operation to a suitable value. When the lamp is not lit, the full supply voltage appears across the tuned circuit of the primary 16 and the capacitor 19. Since the inductance of any winding of an iron core transformer varies with the current passing through it, the capacitor 19 is chosen so that this capacitor and the primary 16 resonate only when full line voltage appears across leads 13 and 14. A large voltage is then produced across the primary 16 at resonance and this voltage is transformed and multiplied by the action of the transformer 17 so that a voltage several times that of the source 12 appears across the secondary 18.

The high voltage of the secondary 18 causes the spark gap 22 to break down and the loop to oscillate, thus producing high frequency voltages. The high frequency oscillations produced in the loop 20 appear across the 2,708,251 Patented May 10, 1955 inductive ballast 15 and are superimposed on the alternating voltage from the source 12. Although the voltage of the source 12 is insufficient in itself to start lamp 11, the addition of the high fiequency voltages ionizes the lamp sutficiently to cause it to light. Ionization is probably due to the rapid oscillation of the gas or vapor molecules caused by the rapidly reversing voltage applied across the lamp.

When the spark gap arcs and the lamp 11 conducts, a large current is caused to flow through the ballast 15 which then produces a voltage drop reducing the voltage across the lamp to its operating value. At the same time, since the voltage available across the leads 13 and 14 is less than before, less current flows through the primary 16, its inductance changes, and it drops out of resonance with the capacitor 19.

It can be seen from the foregoing description that the new circuit is automatic in its operation and since no moving parts are required, maintenance costs are kept low. This circuit was found to instantly start lamps consistently at temperatures as low as 40 degrees centigrade.

Obviously, many modifications and variations of this invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A starting circuit for a lamp which contains an ionizable atmosphere, said circuit comprising a source of alternating current for said lamp, a ballast in series between said source and said lamp, a transformer having a primary and a secondary, a tuned circuit connected across said lamp, said tuned circuit comprising said primary and a capacitor connected in series, whereby said tuned circuit resonates at the frequency and voltage of said source, an oscillatory loop circuit connected across said ballast, said loop circuit comprising said secondary and a spark gap in series therewith, each said secondary and said spark gap having a capacitor in parallel therewith, and means for applying the output of said oscillatory loop circuit to said lamp.

2. A starting circuit for a lamp which contains an ionizable atmosphere, said circuit comprising a source of alternating current for said lam an inductive ballast in series between said source and said lamp, an iron-core step-up transformer having a primary and a secondary, a tuned circuit connected across said lamp, said tuned circuit comprising said primary and a capacitor connected in series, whereby said tuned circuit resonates at the frequency and voltage of said source, and a loop circuit connected across said ballast, said loop circuit comprising said secondary and a spark-gap in series therewith, each of said secondary and said spark-gap having a capacitor connected in parallel therewith chosen to resonate with said secondary and said ballast at a high frequency.

3. A starting circuit for a lamp which contains an ionizable atmosphere, said circuit comprising a source of alternating current for said lamp, an iron-core step-up transformer having a primary and a secondary, a tuned circuit connected across said lamp, said tuned circuit comprising said primary and a capacitor connected in series, which tuned circuit resonates at the frequency and voltage of said source, an inductive ballast connected in series between said source and said lamp, the impedance of said ballast being such that upon conduction of said lamp the voltage applied to said lamp and to said tuned circuit is reduced causing said tuned circuit to cease reso nating, and an oscillatory loop circuit connected across said ballast, said loop circuit comprising said secondary and a spark-gap connected in series, each said secondary 3 7V V and said spark-gap having a capacitor connected in parallel therewith. 7

4. In an energizing circuit for a lamp which contains an ionizable atmosphere, a starting circuit which comprises a transformer having a primary and a secondary which are'electrically separate from each other, an oscillatory circuit comprising said secondary and an elecwith alternatingcurrent, an oscillatory loop, said loop comprising said secondary and an electric discharge device in series, each said secondary and said discharge device having a capacitor in parallel therewith, and means for applying the output of said oscillatory loop across said lamp.

6. In an energizing circuit for a lamp which contains an ionizable atmosphere, a starting circuit comprising an iron-core step-up transformer having a primary and a secondary which are electrically separate from each other, a tuning capacitor in series with said primary, means to energize said primary with an alternating current, an oscillatory loop, said loop comprising said secondary and a spark-gap in series therewith, each said secondary and said spark-gap having a capacitor in parallel therewith,

and means for applying the output of said oscillatory loop across said lamp'whereby high frequency voltages are added to the energizing voltage across said lamp to start the lamp.

References Cited in the file of this patent UNITED STATES PATENTS Marbury Mar. 28, 1939 Pakala July 18,1950 

